Many consumer and industrial vehicles use automatic transmissions filled with automatic transmission fluid (ATF) as the working fluid and to aid in cooling the transmission. In typical configurations, automatic transmissions are equipped with a cooling system, such as an oil cooler, that may be located, for instance, inside an automobile radiator. The automatic transmission fluid is cycled through the oil cooler to regulate its temperature and then back into the transmission in order to keep the transmission cool.
The importance of maintaining fresh and clean transmission fluid is essential in keeping the transmission cool. At regular intervals, the automatic transmission fluid should be removed from the transmission and replaced with fresh fluid. Lack of proper service can cause transmission problems due to the fact that old ATF may no longer meet the manufacturer's specification for performance against rust or harmful attack by corrosive acids that can lead to a breakdown of the metal and aluminum parts in the vehicle's oil cooler or transmission. Furthermore, entrained contaminants and debris contained within old ATF, not fully removed by the transmission's filter assembly, can clog the oil cooler, the result of which is that proper ATF flow through the oil cooler and to the transmission is prevented. Improper ATF flow can cause the transmission to overheat and produce serious, if not, permanent damage.
Many conventional machines and methodologies presently exist for withdrawing the used ATF from an automotive automatic transmission while simultaneously replacing the used fluid with new fluid. These devices and methods are a response to the widely-held recognition that simply dropping the pan from an automatic transmission while doing a filter change (or draining the pan of those transmissions fitted with a drain plug) and then refilling the transmission to the proper level with new fluid results in more than half of the old contaminated ATF remaining in the transmission.
Such is the case because, for example, the clutch actuators, control valves, pump(s), ATF cooler and connecting conduits, and torque converter of the transmission still hold old ATF. In order to extract this old ATF from the transmission, the vehicle engine and transmission must be operated while a fluid exchange for the transmission is in progress.
The vehicle engine can be run with the transmission in “neutral” or “park”, with most of the old ATF being exchanged in this way (i.e., without the drive wheels spinning or the transmission clutches being cycled). In this latter case, the old ATF will still be flushed from the torque converter, ATF cooler, and connecting conduits of the transmission system.
Unfortunately, this operation of the vehicle engine creates a risk that the transmission can be damaged or destroyed by dry running. That is, if the old transmission fluid is drained out, and the transmission is not simultaneously refilled with sufficient new fluid so that the fluid level in the transmission drops too low, then the transmission can be damaged by dry running. In this case, the new transmission fluid may be allowed to partially or completely drain out (perhaps while an attendant is distracted or absent for some reason), and the transmission can be damaged. To be done safely, this method requires full-time attention to both monitor the draining ATF and to infuse new ATF back into the transmission. Obviously, this method can be both labor intensive and prone to error.
In other situations, the supply of new ATF available to the service machine may be inadequate or may have been allowed to run completely out of the service machine to begin with. (For example, the attendant may not check to see that a reservoir for new ATF actually holds an adequate supply.) Again, a sufficient infusion of new ATF into the transmission may not take place during the service procedure, possibly resulting in damage to the vehicle transmission.
Furthermore, an external power failure to the transmission service machine may occur during the service process, with the vehicle under service still running. This may result in the vehicle running without sufficient ATF in the transmission or with its external transmission cooler loop open and the fluid from the transmission being pumped to waste. Again, transmission damage can result unless an attendant catches this situation early enough to prevent sufficient damage.
Accordingly, a desire and a recognized need exists to safely and economically effect the replacement of used ATF with new ATF in an automatic transmission. Unfortunately, many of the machines and methods presently existing for this purpose suffer from one or more of the deficiencies identified above. Additionally, such machines and methods are complex in their construction and operation.